Wretch wrote:
> Greetings -- I'm trying to get Mathematica to do an integral that
> appears regularly in plasma physics problems. It appears to give the
> right answer, but it's always accompanied with an annoying error
> message whose roots are a bit vague. Here is the function to be
> integrated:
>
> f = -2 v Exp[-v^2] over the v-interval (-1,2)
>
> The answer should be about -.34956 (according to an IMSL subroutine)
>
> Here's the mathematica input and output:
>
> In[1]:=NIntegrate[-2 v Exp[-v^2],{v,-1,2}] Out[1]:=Out[99]=-0.349564
I don't know what version of mathematica you are using or on what
platform, but
version 3.0 under win95 on a PC, gives no message when using "Intergate"
or "NIntegrate".
"The answer should be about -.34956 (according to an IMSL subroutine)"
You don't need an IMSL routine to tell you that! The integral is such a
simple
one, after all the integral of -2vExp-v^2] is just Exp[-v^2]. Put in the
limits
and you'll get 1/e^4-1/e.
Cheers,
Bill